Water heating systems of the heat



Sept. 6 1955 I w. c. SILVA 2,716,866

WATER HEATING SYSTEMS OF THE HEAT PUMP TYPE Filed May 27, 1953 Fig 2 Fig 3 //0 v A 6. POWER SOURCE IN V EN TOR. William C. Silva United States Patent WATER HEATING SYSTEMS OF THE HEAT PUMP TYPE William Charles Silva, Chicago, Ill., assignor to General Electric Company, a corporation of New York Application May 27, 1953, Serial No. 357,767

12 Claims. (Cl. 62-4) The present invention relates to water heating systems and more particularly to heat pump water heaters.

A conventional heat pump Water heater comprises an upstanding hot water storage tank having a cold water inlet connection communicating with the lower portion thereof and a hot water outlet connection communicating with the upper portion thereof, as well as associated refrigeration apparatus of the compressor-condenserevaporator type. In the arrangement, the condenser is immersed in the water in the tank and is distributed substantially uniformly from the top to the bottom of the tank.

While a conventional heat pump water heater of the character described is reasonably satisfactory in operation, it is subject to several criticisms. In the first place, there is a hazard of contaminating with refrigerant the water supply system connected to the hot water storage tank in the event of a rupture of the refrigerant condenser, since the condenser is directly immersed in the water stored in the tank. In the second place, the water heater does not have a desirable temperature recovery characteristic, since the refrigerant condenser is substantially uniformly distributed from the top to the bottom of the hot water storage tank so that a long operating time interval is required to obtain hot water at a useable temperature in the upper portion of the tank.

Accordingly, it is a general object of the present invention to provide a heat pump water heater of improved construction and arrangement so that there is no hazard of contaminating with refrigerant the water supply system connected to the hot water storage tank in the event of a leak of the refrigerant from the refrigerant condenser that is arranged in heat exchange relation with the tank and so that the upper portion of the tank has a rapid complete temperature recovery characteristic.

Another object of the invention is to provide in a heat pump water heater, an improved arrangement and disposition of first and second refrigerant condensers positioned in good heat exchange relation with respective upper and lower portions of the hot water storage tank, and an improved thermal control system for the refrigeration apparatus so that all of the compressed gaseous refrigerant from the refrigerant compressor is delivered to the first condenser until a complete temperature recovery of the water in the upper portion of the tank is obtained and so that then all of the compressed refrigerant from the refrigerant compressor is delivered to the second condenser until a complete temperature recovery of the water in the lower portion of the tank is obtained.

A further object of the invention is to provide an improved heat pump water heater of the character described, wherein first and second tank thermostats are arranged in good heat exchange relation with respective upper and lower portions of the hot Water storage tank and respectively positioned above and in spaced-apart relation with respect to the first and second refrigerant condensers so as to provide the temperature control arrangement described.

tages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing in which:

Figure 1 is a partial vertical sectional view of a heat pump Water heater embodying the present invention;

Fig. 2 is an enlarged fragmentary vertical sectional view of a portion of the upper refrigerant condenser and the upstanding side Wall of the hot water storage tank, taken in the direction of the arrows along the line 2-2 in Fig. 1; and

Fig. 3 is a combined electrical and mechanical diagram of the thermal control system incorporated in the heat pump water heater of Fig. 1;

Referring now to Fig. l of the drawing, the water heating system there illustrated and embodying the features of the present invention essentially comprises a heat pump water heater including a hot water storage tank 11 provided with an upstanding substantially cylindrical side Wall 12 having top and bottom end walls or heads 13 and 14. A cold Water inlet connection or spud 15 is secured in liquid-tight relation with an opening provided in the central portion of the bottom head 14 and is connected to a cold water inlet pipe 16 communicating with a suitable cold Water supply system, not shown; and a hot water outlet connection or spud 17 is secured in liquid-tight relation with an opening provided in the cen tral portion of the top head 13 and is connected to a hot water outlet pipe 18 communicating with hot water plumbing, not shown.

Also the water heater 10 comprises refrigeration apparatus of the sealed compressor-condenser-evaporator type including a motor compressor unit sealed in a casing 19, the drive motor of this unit being indicated at 20. Also this refrigeration apparatus includes an evaporator 21, a receiver 22, an expansion valve 23 and first and second condensers 24 and 25, respectively, the condensers 24 and 25 being arranged in good heat exchange relationship with respective upper and lower portions of the cylindrical side wall 12 of the tank 11, as described more fully hereinafter. Preferably the motor compressor unit 19, the evaporator 21, the receiver 22, and the expansion valve 23 are arranged above the top head 13 of the tank 11 and are carried upon a platform 26 supported thereby by suitable brackets 27. Also the platform 26 carries a fan 28 operated by an electric motor 29, the fan 28 being operatively associated with the elements 19, 22 and 21, as explained more fully hereinafter. Further, the tank 11 is provided with a plurality of supporting feet 30 that are suitably attached to the bottom head 14, in a manner not shown; and the water heater 10 is provided with an enclosing casing 31 formed of sheet metal, or the like, and defining a lower compartment 32 housing the tank 11 and the condensers 24 and 25 and an upper compartment 33 housing the elements 19, etc., carried by the platform 26. Also a layer of thermal insulating material 34, fiber glass or the like, is arranged within the compartment 32 below the platform 26 and embedding the tank 11 and the condensers 24 and 25.

The exhaust port of the motor compressor unit 19 is connected to a conduit 35 that extends downwardly from the compartment 33 into the compartment 32; which conduit 35 is arranged tov supply compressed gaseous refrigerant to the condensers 24 and via first and second valves 36 and 37, respectively. The compressed gaseous refrigerant is selectively supplied to the condensers 24 and 25, as explained more fully hereinafter; and the liquified refrigerant from the condensers 24 and 25 is con- I ductedviataconduit 38 back into the compartment 33 and into the receiver 22. The receiver 22 is directly connected to the expansion valve 23; and the expansion valve 23 is directly connected by a discharge tube 39 to the inlet of the evaporator 21. Finally, the outlet of the evaporator 21 is connected via a conduit 40 back to the motor compressor unit 19. In the operation of the water heater 10,.the fan motor 29 effects operation of the fan 28 so that a current of air is circulated through the compartment 33 over the motor compressor unit 19, the receiver 22 and the evaporator 21, thereby to supply heat to the evaporator 21,.the opposite sides of the casing 31 being provided with sets of louvers 41 and 42 to accommodate the passage of the current of air therethrough; Also operation of the drive motor 20 effects operation of the compressor, not shown, whereby the refrigerant is compressed and delivered into the conduit fromtwhich it is conducted into one or the other of the condensers 24 or 25. The liquified refrigerant from the condenser'24 or 25 is conducted via the conduit 38 into thereceiver 22; and thencethe liquified refrigerant is expanded by the expansion valve 23. into the discharge tube. 39'effecting injection thereof into the evaporator 21.

The liquidirefrigerant is expanded fully in the vapor 21 effecting the absorption of heat from the current of air passing thereover; and. the resulting expanded gaseous refrigerant is returned via the conduit back to the moton compressor unit 19-to complete the cycle.

Preferably the tank 10 is essentially formed of sheet steeland is provided with continuous inside and'outside galvanized coatings; and asillustrated in Fig. 2, the side wall 12 of the tank 11 comprises thesteel sheet 43 provided with the insideand-outside galvanized coatings 44 and 45; respectively. The condenser 24 essentially consists of a plurality of flattened coils 46 constituting a helicaltube extending around the'adjacent upper portion of thecylindrical sidewall-12in good heat exchange relation therewith continuously between the valve 36 and the conduit 38; and'likewise, the condenser 25essentiallyconsists of'a plurality of flattened coils constituting a helical tube-extending aroundthe adjacent lower portion of the cylindrical sidewall 12 inlgood heatv exchange relation therewith continuously between the valve 37. and'the conduit' 38.. The spaces between the coils 46 comprising the condenser 241are filledwith fused metal 47- (solder, etc.) in order'to provide. a composite heat shoe in good heatexchangerelation with the. adjacent upper portion of the side wall 12; and likewise,.the' condenser'25 is of r identical construction providing. a composite heat shoe in good heat exchange relation with the adjacent lower portion of the side wall 12;

As a constructional example, the hot water storageltank 11 may have a capacity of 40 gallons;.whereby it may have anoutside diameter of approximately 16" and a height" between the crowns of the top and bottom heads 13-and14 of approximately 48". In this case, referring to Fig. 1, the distance A-between the'crown of the bottom head 14 and the lower endof the condenser 25 may be 2"; the condenser 25 may comprise about21 turns of the tube such that the distance 13 between the bottom and the-top thereof is about 10"; thedistance B between the top of the condenser 25 and the bottom of the'condenser 24: may be; about 14"; the condenser24 may comprise about21 turns of the tube. such that the distance D between the bottom and the top thereof is about 10"; and the;distance E;between thetop of the condenser 24 and the crownof the. top. head l3 may. be about 12". In this constructional example, vthescondenser 24"covers an area 4. of about 20% of the total area of the side wall 12 adjacent to. the. upper. portionthereof; and similarly, the condenser 25 covers an area of about 20% of the total area of the side wall 12 adjacent to the lower portion thereof. Moreover, the refrigerant compressor should be of about /2 ton capacity in order to provide an appropriate heating capacity for the hot water storage tank 11; and in the arrangement, the compressed gaseous refrigerant in the conduit 35 may have a temperature of about 200 F. and the liquid refrigerant in the conduit 38 may have a temperature of about 165 F.

A first tank thermostat 48 is suitably secured to the upper portion of the side wall 12 just above the top of the condenser 24 so that it is disposed in'good heat exchange relation with the side wall 12 and not directly influenced by the temperature of the condenser 24 in order that the tank thermostat 4-3 is effectively responsive to the temperature of the water in the upper portion of the tank 11. Similarly, a second tank thermostat 49 is suitably secured to the lower portion of the side wall 12 just above the top of the condenser 25 so that it is disposed in good-heat exchange relation withtheside walls12 and not directly influenced by the temperature of thecondenser 25in order that the tank thermostat Wis-effectively responsive to the temperature of the water in the lower portion of the tank 11. Preferably, each of the tank thermostats 48 and 49 is of the general construction and arrangement of that disclosed in U. S. Patent No. 2,585,340,- granted on February 12, 1952, to Nicholas Miller; each of the tank thermostats 48 and 49 being of the snap-acting type having a cold position and a hot position and being manually adjustable to accommodate the variable setting of the control temperature thereof. Specifically, the adjustable thermostat 48 may be preset so that it is operated from its cold position into its hot position when the water in the adjacent upper portion of the tank 11 is at a desired storage temperature of approximately 150 F., the thermostat 48 being'operated from its hot position'back into its cold position in response to a temperature slightly below 150 F. of the water in the adjacent upper portion of the tank 11. Similarly, the adjustable thermostat 49 may be preset so that it is operated from its cold position into its hot position when the water in the adjacent lower portion of the tank 11 is at a desired storage temperature of approximately 150" F., the thermostat 49 being operated from its hot position back into its cold position in response to a temperature slightly below l50 F. of the water in the adjacentlower portion of the tank 11.

As illustratedin Fig. 3, the electric control circuit for the water heater 10 comprises a source of current supply of 110 volts single phase, A. C., as well as a manually operable master switch 50. The valve 36 is of the electromagnetically operated type including flow control mechanism 51 normally biased into a closed position and operative into an'open position by an associatedsolenoid 52. Likewise, the valve 37 is of the electromagnetically operated type including flow control mechanism 53 normally biased into a closed position and operative into an open position by an associated'solenoid54. The thermostatic switch 48 is of the single-pole double-throw type including a contact bridging member 55 movable between upper and lower positions respectively controlling upper and lower pairs of contacts; while the thermostatic switch 49'is of the single-pole single-throw type including-a contact bridging member 56 movable to control an associated pair of contacts.

Considering now the overall operation of the water heater ltl and assuming that the storage tank 11 is compietely filled with cold water at an ambient temperature of 50 F, the thermostatic switches 48 and 49 occupy their cold positions. More particularly, the thermostatic S\VliCh 43' occupiesits cold position so'that the. contact bridging member 55 closes'theupper pair ofscontacts preparing the solenoid 52; and: the'thermostatic switch 49 occupies its cold position so that the contact bridging member 56 closes the associated pair of contacts preparing the compressor drive motor and the fan motor 29. At this time, when the master switch 50 is closed, operation of the compressor drive motor 20 and the fan motor 29 are initiated. Also the solenoid 52 is energized so that the flow control mechanism 51 of the valve 36 is operated from its closed position into its open position; however, the solenoid 54 is de-energized so that the flow control mechanism 53 of the valve 37 remains in its closed position. Accordingly, the upper condenser 24 is connected to the conduit 35 and the lower condenser 25 is disconnected from the conduit 35, whereby the operating compressor drive motor 20 effects circulation of the refrigerant through the circuit including the upper condenser 24 and excluding the lower condenser 25. The operating fan motor 29 causes the circulation of the current of air through the compartment 33 so that heat is absorbed by the evaporator 21; the heat being dissipated by the upper condenser 24 into the adjacent upper portion of the tank 11, whereby the water in the upper portion of tank 11 is heated. After an appropriate time interval the water in the upper portion of tank 11 is heated from the ambient temperature of 50 F. to the preset control temperature of 150 F., whereby the upper thermostat 48 is operated from its cold position into its hot position so that the contact bridging member 55 opens the upper pair of contacts and closes the lower pair of contacts respectively deenergizing the solenoid 52 and energiz ing the solenoid 54. When the solenoid 52 is thus deenergized, the flow control mechanism 51 of the valve 36 is returned back into its closed position; and when the solenoid 54 is thus energized, the flow control mechanism 53 of the valve 37 is operated into its open position. Accordingly, at this time, the upper condenser 24 is disconnected from the conduit and the lower condenser 25 is connected to the conduit 35. Operation of the compressor drive motor 20 and the fan motor 29 are continued, whereby the water in the lower portion of the tank 11 is heated. After an additional and considerable time interval, the water in the lower portion of the tank 11 is heated from the ambient temperature of 50 F. to the preset control temperature of 150 F., whereby the lower thermostat 49 is operated from its cold position into its hot position so that the contact bridging member 56 opens the associated pair of contacts de-energizing the solenoid 54, the compressor drive motor 20 and the fan motor 29. When the solenoid 54 is thus de-energized, the flow control mechanism 53 of the valve 37 is returned back into its closed position. At this time, operation of the motors 20 and 29 are arrested since the tank 11 is now completely filled with hot water at the preset proper storage temperature of 150 F.

Thereafter in the event of the draw-off of a modest amount of hot water from the upper portion of the tank 11 via the outlet pipe 18, cold water via the inlet pipe 16 is supplied into the lower portion of the tank 11. Accordingly at this time, hot water at the preset proper storage temperature of 150 F. remains in the upper portion of the tank 11 so that the upper thermostat 48 remains in its hot position; however, the cold water introduced into the lower portion of the tank 11 brings about mixing with the hot water therein and the consequent production of a warm water condition in the lower portion of the tank 11. In this case, the Warm water in the lower portion of the tank 11 brings about reoperation of the lower thermostat 49 from its hot position back into its cold position so that operation of the compressor drive motor 20 and the fan motor 29 are initiated and the solenoid 54 is again energized in order again to operate the flow control mechanism 53 of the valve 37 into its open position. Thus, at this time, the compressed gaseous refrigerant is again supplied to the lower condenser 25 for an appropriate time interval until the water in the lower portion of the tank 11 is again heated to the preset control temperature of 150 F., whereby the lower thermostat 49 is again operated from its cold position back into its hot 'position so that operation of the compressor motor 20 and the fan motor 29 are arrested and the solenoid 54 is deenergized bringing about the return of the flow control mechanism 53 of the valve 37 back into its closed position.

In the water heater 10 of the specification set forth above, a full tank of gallons of cold water at the ambient temperaure of F., may be heated to the preset control temperature of 150 F. in a time interval of 6 hours in a room at an ambient temperature of F and 40% relative humidity. While the complete temperature recovery time interval of the water heater 10 is 6 hours from the ambient temperature of 50 F., as noted above, the upper thermostat 48 is influenced only by the upper quarter of the volume of the tank 11, whereby the upper thermostat 48 is operated from its cold position into its hot position in a time interval of only 1 /2 hours, the lower thermostat 49 being operated from its cold position into its hot position after an additional time interval of 4 /2 hours.

Accordingly, it will be appreciated that the temperature recovery characteristic of the water heater 10 is very advantageous as the upper portion thereof containing about 10 gallons of water may be heated from the ambient temperature of 50 F. to the preset control temperature of F. in only the short time interval of 1 /2 hours; whereby, there is adequate hot water for normal usage in the tank 11 after only this short time interval of operation of the water heater 10. This advantageous result is brought about by the preferential supply of the compressed gaseous refrigerant from the compressor into the upper condenser 24, to the exclusion of the lower condenser 25, until the water in the upper portion of the tank 11 is heated to the preset control temperature of 150 F. to provide the modest amount of usable hot water in the upper portion of the tank 11.

Further, it will be appreciated that since the coils of the condensers 24 and 25 are exposed to the exterior and are isolated from the water contained in the tank 11 by the side wall 12, there is no danger of contamination with refrigerant of the water contained in the tank 11, and consequently the water supply system, in the event of a leak of refrigerant from either of the condensers 24 and 25. Accordingly, the hazard of refrigerant contamination of the hot water stored in the tank 11 is completely eliminated.

In view of the foregoing, it is apparent that there has been provided a heat pump water heater of improved construction and arrangement'that eliminates the usual hazard of contaminating with refrigerant the hot water contained in the storage tank in the event of a leak of refrigerant from the associated condenser, and that has a highly advantageous temperature recovery characteristic.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a water heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged exteriorly of and in good heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged exteriorly of and in good heat exchange relation with the lower portion of said tank, a refrigerant compressor operative to compress expanded gaseous refrigerant, first thermal means selectively governed by the temperature of the water in the upper portion of said tank for conducting compressed gaseous refrigerant from said compressor selectively into said first and second condensers, second thermal means selectively governed by the temperature of the water in the lower portion of said tank for selectively operating said compressor, a refrigerant evaporator, means for expanding liquid refrigerant from said first and second condensers into said evaporator, and means for conducting expanded gaseous refrigerant from said evaporator back into said compressor.

2. In a water heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged exteriorly of and in good heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged exteriorly of and in good heat exchange relation with the lower portion of said tank, a first thermostat arranged exteriorly of said tank and in good heat exchange relation with a first portion thereof disposed above said first condenser, a second thermostat arranged exteriorly of said tank and in good heat exchange relation with a second portion thereof disposed above said second condenser, a refrigerant compressor operative to compress expanded gaseous refrigerant, valve mechanism selectively governed by said first thermostat for conducting compressed gaseous refrigerant from said compressor selectively into said first and second condensers, a motor selectively governed by said second thermostat for selectively operating said compressor, a refrigerant evaporator, means for expanding liquid refrigerant from said first and second condensers into said evaporator, and means for conducting expanded gaseous refrigerant from said evaporator back into said compressor.

3. In a water heating system including a hot water storage tank provided with an upstanding side wall and top and bottom heads, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged exteriorly of and in good heat exchange relation with the upper portion of said side wall and covering about 20% of the area thereof, a second refrigerant condenser arranged exteriorly of and in good heat exchange relation with the lower portion of said side wall and covering about 20% of the area thereof, a refrigerant compressor operative to compress expanded gaseous refrigerant, first thermal means selectively governed by the temperature of the water in the upper portion of said tank for conducting compressed gaseous refrigerant from said compressor selectively into said first and second condensers, second thermal means selectively governed by the temperature of the water in the lower portion of said tank for selectively operating said compressor, a refrigerant evaporator, means for expanding liquid refrigerant from said first and second condensers into said evaporator, and means for conducting expanded gaseous refrigerant from said evaporator back into said compressor.

4. In a water heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged in heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged in heat exchange relation with the lower portion of said tank, first thermal means responsive to a low temperature of the water in the upper portion of said tank for conducting compressed gaseous refrigerant from said compressor into said first condenser and responsive to a high temperature of the water in the upper portion of said tank for conducting compressed gaseous refrigerant from said compressor into said second condenser, second thermal means responsive to a low temperature of the water in the lower portion of said tank for initiating operation of said compressor and responsive to a high temperature of the water in the lower portion of said tank for arresting operation of said compressor, a refrigerant evaporator, means for expanding liquid re frigerant from said first and second condensers into said evaporator, and means for conducting expanded gaseous refrigerant from said evaporator back into said compressor.

5. In awater heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged in heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged in heat exchange relation with the lower portion of said tank, a first tank thermostat responsive to the temperature of the water in the upper portion of said tank, a second tank thermostat responsive to the temperature of the water in the lower portion of said tank, a refrigerant compressor operative to compress expanded gaseous refrigerant, a motor for operating said compressor, a first conduit for conducting compressed gaseous refrigerant from said compressor, valve mechanism operative between first and second positions connecting said first conduit respectively to said first and second condensers, a second conduit for conducting liquid refrigerant from said first and second condensers, a refrigerant evaporator, means for expanding liquid refrigerant from said second conduit into said evaporator, a third conduit for conducting expanded gaseous refrigerant from said evaporator back into said compressor, means governed by said first tank thermostat for selectively operating said valve mechanism between its first and second positions, and means governed by said second tank thermostat for selectively operating said motor.

6. The water heating system combination set forth in claim 5, wherein each of said first and second condensers essentially comprises a section of tubing coiled around the outside of said tank in good heat exchange relation therewith.

7. In a water heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged in heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged in heat exchange relation with the lower portion of said tank, a first tank thermostat responsive to the temperature of the water in the upper portion of said tank, a second tank thermostat responsive to the temperature of the water in the lower portion of said tank, a refrigerant compressor mounted upon the top of said tank and operative to compress expanded gaseous refrigerant, a first conduit for conducting compressed gaseous refrigerant from said compressor, valve mechanism operative to connect said first conduit selectively to said first and second condensers, a second conduit for conducting liquid refrigerant from said first and second condensers, a refrigerant evaporator mounted upon the top of said tank, means for expanding liquid refrigerant from said second conduit into said evaporator, a third conduit for conducting expanded gaseous refrigerant from said evaporator back into said compressor, a body of heat insulation embedding said tank and said first and second condensers, a casing housing said body of heat insulation and said tank and said first and second condensers and said compressor and said evaporator and said valve mechanism and said conduits, means governed by said first tank thermostat for selectively operating said valve mechanism, and means 9 governed by said second tank thermostat for selectively operating said compressor.

8. In a Water heating system including an upstanding hot Water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged in heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged in heat exchange relation with the lower portion of said tank, a first tank thermostat responsive to the temperature of the water in the upper portion of said tank, a second tank thermostat responsive to the temperature of the water in the lower portion of said tank, a refrigerant compressor operative to compress expanded gaseous refrigerant, a first electric motor for operating said compressor, a first conduit for conducting compressed gaseous refrigerant from said compressor, valve mechanism operative to connect said first conduit selectively to said first and second condensers, a second conduit for conducting liquid refrigerant from said first and second condensers, a refrigerant evaporator,

a second electric motor for circulating a current of air over said evaporator in heat exchange relation therewith, means for expanding liquid refrigerant from said second conduit into said evaporator, a third conduit for conducting expanded gaseous refrigerant from said evaporator back into said compressor, means governed by said first tank thermostat for selectively operating said valve mechanism, and means governed by said second tank thermostat for selectively operating together said first and second motors.

9. In a water heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged in heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged in heat exchange relation with the lower portion of said tank, a first tank thermostat responsive to the temperature of the water in the upper portion of said tank and having corresponding cold and hot positions, a second tank thermostat responsive to the temperature of the water in the lower portion of said tank and having corresponding cold and hot positions, a refrigerant compressor operative to compress expanded gaseous refrigerant, a first conduit for conducting compressed gaseous refrigerant from said compressor, valve mechanism having a first position connecting said first conduit to said first condenser and disconnecting said first conduit from said second condenser and a second position connecting said first conduit to said second condenser and disconnecting said first conduit from said first condenser, a second conduit for conducting liquid refrigerant from said first and second condensers, a refrigerant evaporator, means for expanding liquid refrigerant from said second conduit into said evaporator, a third conduit for conducting expanded gaseous refrigerant from said evaporator back into said compressor, means governed by said first tank thermostat in its respective cold and hot positions for operating said valve mechanism into its respective first and second positions, and means governed by said second tank thermostat in its respective cold and hot positions for initiating and for arresting respectively operation of said compressor.

10.- The water heating system combination set forth in claim 9, wherein each of said tank thermostats is of the snap-action type and is adjustable selectively to establish the control temperature at which operation thereof between its cold and hot positions takes place.

11. In a water heating system including an upstanding hot water storage tank, a cold water inlet connection communicating with the lower portion of said tank, and a hot water outlet connection communicating with the upper portion of said tank; the combination comprising a first refrigerant condenser arranged in heat exchange relation with the upper portion of said tank, a second refrigerant condenser arranged in heat exchange relation with the lower portion of said tank, a first tank thermostat responsive to the temperature of the water in the upper portion of said tank and having corresponding cold and hot positions, a second tank thermostat responsive to the temperature of the water in the lower portion of said tank and having corresponding cold and hot positions, a refrigerant compressor operative to compress expanded gaseous refrigerant, a first conduit for conducting compressed gaseous refrigerant from said compressor, a first valve for selectively connecting said first conduit to said first condenser, a second valve for selectively connecting said first conduit to said second condenser, a second conduit for conducting liquid refrigerant from said first and second condensers, a refrigerant evaporator, means for expanding liquid refrigerant from said second conduit into said evaporator, a third conduit for conducting expanded gaseous refrigerant from said evaporator back into said compressor, means governed by said first tank thermostat in its cold position for operating said first valve into its open position and for operating said second valve into its closed position and governed by said first tank thermostat in its hot position for operating said first valve into its closed position and for operating said second valve into its open position, and means governed by said second tank thermostat in its respective cold and hot positions for initiating and for arresting respectively operation of said compressor.

12. The water heating system combination set forth in claim 11, wherein each of said valves is of the electromagnetically operated type and is normally biased into its closed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,996,625 Pendleton Apr. 2, 1935 2,095,017 Wilkes Oct. 5, 1937 2,415,965 Osterheld Feb. 18, 1947 2,512,066 Linfor June 20, 1950 2,516,093 Ruff July 18, 1950 2,516,094 Ruif July 18, 1950 2,585,340 Miller Feb. 12, 1952 

